Apple has released a minor update to OS X Mountain Lion, fixing "an issue with Keychain that can affect 2012 Mac systems." The update weighs in at 26.65MB and can be downloaded through Apple's support site or the Mac App Store.

Quote:

About OS X Mountain Lion 10.8.2 Supplemental Update 2.0

This update addresses an issue with Keychain that can affect 2012 Mac systems.

Apple has released a minor update to OS X Mountain Lion, fixing "an issue with Keychain that can affect 2012 Mac systems." The update weighs in at 26.65MB and can be downloaded through Apple's support site or the Mac App Store.
Apple previously released OS X v10.8.2 Supplemental Update 1.0 at the beginning of October.

They did that last week. At least that's what they were addressing. On my rMBP I only noticed slowdown once before that, luckily, now I play GW2 without a problem. Most probably the problem is with other games.

I'm happy about this update also, this keychain issue has been driving me nuts.

I have a 2012 Mini that I was able to update to 10.8.2 before they pulled it. Software update did not find this new update, but I was able to download and install from the Apple download site - same issue with the previous 10.8.2 installer.

Apple really seems to keep messing this one up in many ways. Is software update through the App Store usually this wrong?

Apple has released a minor update to OS X Mountain Lion, fixing "an issue with Keychain that can affect 2012 Mac systems." The update weighs in at 26.65MB and can be downloaded through Apple's support site or the Mac App Store.
Apple previously released OS X v10.8.2 Supplemental Update 1.0 at the beginning of October.

Odd and mildly irritating that Apple lists this as an update compatible with all machines running 10.8.2, when it appears to only be for 2012 machines. I'm guessing that's why I'm not seeing it on my work computer (a low end Mid-2011 Mac mini) and why I'll likely see it on my Mid 2012 non-retina 15" MacBook Pro.

Though amusing that Apple appears to have so many software glitches with Mountain Lion on these new machines.